Metal to metal sea for extreme temperature applications

ABSTRACT

Disclosed is an electromagnetically operated force motor which positions a valve member with respect to a valve seat to open and close a valve, thereby controlling the flow of fluid through a chamber which is sealed with respect to the force motor. The valve seat is maintained in position by a mechanical bond which provides a fluid-tight seal under extreme temperature conditions, for example, cryogenic applications.

United States Patent Baxter, Jr. 14 1 June 13, 1972 [5 METAL T0 METALSEA FOR 3,107,895 10/1963 Vogeli ..2s1/3s9 EXTREME TEMPERATURE 3,127,9054/1964 Vogeli... .251/359 X APPLICATIONS 3,164,364 H1965 MCCO" ..25 H3343,412,975 11/1968 Kurkjian. .lr.. .....2Sl/362 [72] Inventor: David W.Baxter, Jr., Sylmar, Calif. 3,458,170 7/1969 Vegeli .251/359 X 3,471,12310/1969 Carlson et al.... .251/362 [73] Assgnee' 3,487,823 1/1970 Tarteret al. .251/359 x [22] Filed: Jan. 14, 1970 Primary Evaminer-SamuelScott [2!] Appl' Attorney-Nilsson, Robbins, Wills and Berliner [52] U.S.Cl ..25l/359 [57] ABSTRACT [51] Int. Cl ..Fl6k 51/00, Fl6k 1/226D1sclosed is an electromagnetlcally operated force motor [58] held ofSearch ..251/359, 362, 334, 333, 365 which positions a valve member withrespect to a valve Seat to open and close a valve, thereby controllingthe flow of fluid [56] References Clted through a chamber which issealed with respect to the force UNITED STATES PATENTS motor. The valveseat is maintained in position by a mechanical bond which provides afluid-tight seal under extreme teml,720,486 7/1929 Leipert ..25 l/359 Xperamre conditions, f example, cryogcnic applications 1,795,433 3/1931Leipert ..25l/359 X 3,022,978 2/1962 Kowalski et al ..251/363 X 9Claims, 5 Drawing Figures PATENTEDJUH 13 m2 3, 669.408

FIG. 1.

I NVENTOR DAV/D l/V. B/QXTER, JR.

METAL TO METAL SEA FOR EXTREME TEMPERATURE APPLICATIONS BACKGROUND OFTHE INVENTION In controlling the flow of certain very corrosive andtoxic fluids, such for example as hydrazine, it is necessary to providevalves having zero leakage throughout, including the valve seat andvalve. To obtain the required finishes so as to meet the leakagespecification, cemented carbide metals are used for seats and poppets.Typically, such seats and poppets are brazed in place. However, suchcorrosive fluids attacked and destroyed the brazing metal normallyutilized. Electron beam welding was attempted and could not be usedbecause of the great difference in melting temperature between thecemented carbides and the valve body material and the discovery that thecarbides were caused to crack by the high temperatures involved in theelectron beam welding. Therefore, the normal metal processing techniquesgenerally employed are not available. A technique of swaging a metallicmaterial into grooves formed in the apparatus, as disclosed in U.S.application, Ser. No. 776,928, filed Nov. 19, I968 now U.S. Pat. No.3,559,946 and assigned to the assignee of the present application hasproven successful in overcoming the prior problems except in thoseapplications where extreme temperature conditions persist, such as incryogenic or very high temperatures. Under such ambient temperatureconditions, or cycling between room temperature and such ambients, ithas been found that the swaged metal seals tend to leak.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1illustrates in cross-section a valve structure formed in accordance withthe present invention;

FIG. 2 illustrated in cross-section, the valve seat portion of the valveillustrated in FIG. 1;

FIGS. 3 and 4 illustrate the valvestructure shown in FIG. 2 inintermediate stages of construction; and

FIG. 5 illustrates an alternative embodiment.

DETAILED DESCRIPTION Referring now to FIG. 1, there is generallyillustrated in an elevational view in cross-section anelectromagnetically operated force motor for operating a poppet valveutilized for the control of highly corrosive fluids such as those abovereferred to. Such a valve includes an armature 11 positioned betweenpole pieces 12 which are actuated by coils 13 to which an electricalsignal is applied from a source thereof (not shown). A flapper 14 issealed to a flexure tube 15 at the upper end thereof and the flexuretube is in turn sealed at its upper end 16 to the armature. The lowerend 17 of the flexure tube is sealed to the body 18 of the valve therebycausing the flexure tube to accomplish the functions of sealing theforce motor from the remainder of the valve and also physicallysupporting the flapper l4. Affixed to the lower end of the flapper 14 isa poppet 19 which cooperates with a valve seat 21 to control the flow offluid from a source thereof (not shown) through the valve into an inputport 22 and out through the output port 23 in the direction as shown bythe arrow 24. A valve of the type generally illustrated in FIG. 1, andbriefly described above, is well known in the prior art, as illustrated,

for example, by U.S. Pat. No. 3,373,769 and, therefore, detaileddescription will not be made thereof at the present time. As isdiscussed in U.S. Pat. No. 3,373,769, such a valve is capable of and isspecifically designed for handling highly corrosive fluids of the typeabove referred to either in the form of single or dual poppet valves.

Although the present invention relates generally to such valves, it isspecifically directed to the mechanical retention which is employed inthe construction thereof, such, for example', as retaining the valveseat 21 on the valve body while the valve is subjected to extremetemperature ambients. The construction of the seat 21 is more clearlyillustrated in FIG. 2 to which reference is hereby made.

As is illustrated in FIG. 2, the body 18 of the valve defines a recess26 therein the bottom of which forms a base 27 upon which a first memberin the form, for example, of a valve seat body rests. The seat bodydefines an orifice 29 therethrough which is aligned with an opening 31formed through the valve body 18. The valve seat body also defines avalve seat 32 in the form of a metal surface upon which the poppet 19seats in order to control the flow of fluid through the valve as abovedescribed. After the seat body 28 is thusly positioned in place, it isretained in place mechanically (as opposed to being welded or bolted) bya retainer member 33. The retainer member 33 has an outwardly extendinganchoring surface such as a flange 34 which fits within the recess 26and abuts the wall forming the same. The retainer member 33 is held inplace within the recess 26 by being permanently affixed to the body 18such, for example, as by electron beam welding 35 through a continuousopening 36 provided between the retainer 33 and the body of the valve18. The retainer 33 also includes an inwardly directed flange 37 whichdefines a continuous surface 38. The continuous surface 38 seats uponand mates with a second continuous surface 39 defined by the seat body28. As will be more fully described below, the retainer 33 is placedunder stress thereby to effect a seal between the continuous surfaces 38and 39 of a metal to metal type and also to retain the seat body 28 inplace upon the base 27. As is also illustrated in FIG. 2, a redundantseal is provided by a Teflon washer 41 which is received within aperipheral recess 42 formed within the seat body 28. Teflon is aregistered trademark of Dupont for polytetrafluoroethylene.

The construction of the valve seat shown in FIG. 2 is more clearlyillustrated in FIGS. 3 and 4 to which reference is hereby made. As isshown in FIG. 3, the retainer member 33 includes a wall 43 having aninternal effective dimension d, when taken in the direction of the axisa of the orifice 29 formed through the seat body 28. The seat body 28has a dimension d, also taken along the direction of the axis a. Adimension of the wall 43, as can be seen, is taken from the continuoussurface 38 thereof to the bottom surface 44 while the dimension :1 istaken from the continuous surface 39 to the bottom surface 45 thereof.Thus, it will be noted by reference to FIG. 2 that the bottom surfaces44 and 45 are aligned when the seat is fully constructed and in placeupon the valve body 18. However, the dimensions d and d are chosen insuch a manner that (1 is greater than d by some predetermined amount sothat when the surfaces 44 and 45 are brought into alignment, the flange37 is stressed thereby applying a pre-load upon the seat body 28. Thus,it can be seen thatthe distance between the clamping surfacd 38 and theanchoring surface 34 of the retainer member 33 is shorter before theweld 35 is made than thereafter by an amount d (FIG. 4) to stress theflange 37.

Thus, in construction the Teflon washer like member 41 would be placedinto the periphemal recess 42 after which the seat body 28 would bepositioned upon the base 27. The retainer 33 would then be brought intoplace in the manner illustrated in FIG. 4. Thereafter, the flange 34would be pressed downwardly so that the bottom surfaces 44 and 45 of theretainer 33 and the seat body 28 would each bear against the base 27 andthereby be in alignment. At this point, the weld 35 would be effectedafter which the seat would be permanently and rigidly affixed to thevalve body 18. As a result of bringing the surfaces 44 and 45 intoalignment, the flange 37 would be stressed as is illustrated in FIG. 2,in highly over-emphasized fashion. At the sametime, theTeflon washerlike member 41 would be slightly deformed as a result of the stress alsoas is over-emphasized in illustration for clarity in FIG. 2.

It has been found desirable in most applications to utilize a dimensiondifference d sufiicient to accomplish approximately a 1,000 pounds persquare inch pre-load upon the continuous surface 39 of the seat body atroom temperature. The materials for the seat body 28 and the retainer 33are chosen so that the coefficients of thermal expansion and contractionare such that as the ambient temperature to which the valve is subjectedchanges, the load applied by the continuous surface 38 against thecontinuous surface 39 increases. Thus, if the ambient temperature is toincrease, the coefficient of thermal expansion and contraction of theseat 28 must be greater than that of the retainer 33 while if thetemperature is to decrease, then the coefficient of thermal contractionand expansion of the retainer 33 must be greater than that of the seatbody 28.

As one specific example, assume that the valve is to be utilized in acryogenic application such that the temperature will approach absolutezero. Under these circumstances, the material from which the seat body28 would be constructed would be a cemented tungsten carbide which hasan exceedingly low coefficient of thermal expansion and contraction,Alternatively, one could utilize a ceramic material such as aluminawhich also has an extremely small coefiicient of thermal expansion andcontraction. For the retainer 33 either titanium or lnconel alloy X-750could be utilized. lnconel is a trademark of International NickelCompany and lnconel alloy X-750 is a nickel-chromium alloy having thefollowing composition:

Titanium at 320 F. has a 4 per cent elongation while Incone] alloy X-750has l9 per cent elongation at 320 F. Such percentage of elongationprovides a faster shrinkage rate as the ambient temperature decreasesfor the retainer than for the seat body so as to effect the desiredincrease of stress, as above referred to. It has been determined that aneffective differential between the shrinkage rates of the retainer andthe seat to effect the desired increase in stress as temperature changesis approximately 2 to 1, although such has not been found to beextremely critical.

The cemented tungsten carbide and lnconel alloy X-750 may also be usedin high temperature applications for the seat and retainer respectivelyby arranging the clamping features as illustrated in FIG. 5. The valvebody 51 defines a recess 52 into which a seat body 53 is positioned soas to align openings 54 and 55. The seat body 53 includes a radiallyoutwardly extending flange 56 defining a continuous surface 57 thereon.A retainer member 58 is seated within a recess 59 formed in the valvebody 51 and is rigidly affixed in place as by welding at 61. Theretainer member 58 includes a radially inwardly directed flange 62defining a continuous surface 63. The continuous surfaces 57 and 63 areurged into a metal to metal seal by proper pre-loading through stressingthe retainer member flange 62 during assembly. That is, when theretainer member 58 is fitted in dimension as above outlined such thatthe surface 64 must be forced downwardly into alignment with surface 65before welding. Since the coefficient of thermal expansion andcontraction of lnconel alloy X-750 is such that the length of theretainer increases as ambient temperatures increase, the force appliedby surface 63 against surface 57 increases thereby effecting a betterseal.

What is claimed is:

1. In an apparatus for receiving fluid under pressure, a metal to metaljoint comprising:

a body member having a base;

a first member having a first coefiicient of thermal expansion andcontraction positioned to rest on said base, and includes a firstcontinuous surface area;

a second member having a second coefficient of thermal expansion andcontraction and having an anchoring surface, including a wall,permanently and rigidly affixed to said body and having clamping meansincluding a second continuous clamping surface area extending from saidwall into sealing engagement with said first continuous surface area andsecuring said first member to said base;

the distance between said clamping surface and said anchoring surface ofsaid second member being different before said second member is affixedto said body than after being affixed so that said clamping surfaceextends from said wall substantially orthogonally before and obtuselyafter said second member is affixed to said body, thereby to stress saidclamping means and effect the securing of said first member to saidbase;

said first'coefficient of thermal contraction and expansion beingdifferent from said second coefficient of thermal, thereby to effectgreater clamping force'by said second member as ambient temperaturechanges.

2. Apparatus as defined in claim 1 wherein said wall has a length whichis shorter than the thickness of said first member and the coefficientof thermal contraction and expansion of said second member issubstantially greater than that of said first member.

3. Apparatus as defined in claim 2 which further includes deformablesealing means disposed between said first member and said clampingmeans.

4. Apparatus as defined in claim 3 wherein said deformable sealing meansis a teflon washer like member and said first member defines a groovefor receiving said washer like member.

5. Apparatus as defined in claim 4 wherein said body and said firstmember define aligned orifices.

6. A valve for controlling the flow of fluid under pressure therethroughcomprising:

a metal valve body defining an opening therethrough;

a metal seat member defining an orifice positioned in align ment withsaid opening;

a metal clamping member surrounding said seat member and including awall and a radially inwardly directed flange at one end of said wall,extending into continuous metal to metal contact with said seat memberand an anchoring surface at the other end of said wall permanently andrigidly connected to said body;

the distance between said contact surface of said flange and saidanchoring surface being different before said anchoring surface isaffixed to said body than after being affixed so that said flangeextends substantially orthogonally from said wall before and obtuselyafter said clamping member is affixed to said body;

said flange being thereby stressed, not exceeding its elastic limitthereby effecting a seal between said flange and said seat at saidcontinuous contact therebetween.

7. A valve as defined in claim 6 wherein the coefficients of thermalcontraction and expansion of said clamping member and said seat memberare substantially different thereby to effect a better seal as theambient temperature of said valve changes.

8. A valve as defined in claim 7 wherein said seat member has a firstdimension taken along the axis of said orifice, said clamping memberincludes a body portion having a second dimension taken along a lineparallel to said axis, said second dimension being smaller than saidfirst dimension and the coefficient of thermal expansion and contractionof said seat member being greater than that of said clamping member,thereby effecting a tighter seal when the ambient temperature increases.

1. In an apparatus for receiving fluid under pressure, a metal to metaljoint comprising: a body member having a base; a first member having afirst coefficient of thermal expansion and contraction positioned torest on said base, and includes a first continuous surface area; asecond member having a second coefficient of thermal expansion andcontraction and having an anchoring surface, including a wall,permanently and rigidly affixed to said body and having clamping meansincluding a second continuous clamping surface area extending from saidwall into sealing engagement with said first continuous surface area andsecuring said first member to said base; the distance between saidclamping surface and said anchoring surface of said second member beingdifferent before said second member is affixed to said body than afterbeing affixed so that said clamping surface extends from said wallsubstantially orthogonally before and obtusely after said second memberis affixed to said body, thereby to stress said clamping means andeffect the securing of said first member to said base; said firstcoefficient of thermal contraction and expansion being different fromsaid second coefficient of thermal, thereby to effect greater clampingforce by said second member as ambient temperature changes.
 2. Apparatusas defined in claim 1 wherein said wall has a length which is shorterthan the thickness of said first member and the coefficient of thermalcontraction and expansion of said second member is substantially greaterthan that of said first member.
 3. Apparatus as defined in claim 2 whichfurther includes deformable sealing means disposed between said firstmember and said clamping means.
 4. Apparatus as defined in claim 3wherein said deformable sealing means is a teflon washer like member andsaid first member defines a groove for receiving said washer likemember.
 5. Apparatus as defined in claim 4 wherein said body and saidfirst member define aligned orifices.
 6. A valve for controlling theflow of fluid under pressure therethrough comprising: a metal valve bodydefining an opening therethrough; a metal seat member defining anorifice positioned in alignment with said opening; a metal clampingmember Surrounding said seat member and including a wall and a radiallyinwardly directed flange at one end of said wall, extending intocontinuous metal to metal contact with said seat member and an anchoringsurface at the other end of said wall permanently and rigidly connectedto said body; the distance between said contact surface of said flangeand said anchoring surface being different before said anchoring surfaceis affixed to said body than after being affixed so that said flangeextends substantially orthogonally from said wall before and obtuselyafter said clamping member is affixed to said body; said flange beingthereby stressed, not exceeding its elastic limit thereby effecting aseal between said flange and said seat at said continuous contacttherebetween.
 7. A valve as defined in claim 6 wherein the coefficientsof thermal contraction and expansion of said clamping member and saidseat member are substantially different thereby to effect a better sealas the ambient temperature of said valve changes.
 8. A valve as definedin claim 7 wherein said seat member has a first dimension taken alongthe axis of said orifice, said clamping member includes a body portionhaving a second dimension taken along a line parallel to said axis, saidsecond dimension being shorter than said first dimension and thecoefficient of thermal expansion and contraction of said clamping memberbeing greater than that of said seat member, thereby effecting a tighterseal when the ambient temperature decreases.
 9. A valve as defined inclaim 7 wherein said seat member has a first dimension taken along theaxis of said orifice, said clamping member includes a body portionhaving a second dimension taken along a line parallel to said axis, saidsecond dimension being smaller than said first dimension and thecoefficient of thermal expansion and contraction of said seat memberbeing greater than that of said clamping member, thereby effecting atighter seal when the ambient temperature increases.